A toilet has only a handful of parts, but they get used more than any other fixture in the house. The common complaints are a toilet that runs long after the flush, one that clogs or flushes weakly, water on the floor around the base, and a tank that fills slowly or hisses.
This guide sorts those complaints by cause, shows you what to look at without lifting the tank lid or using tools, flags the few toilet problems that are real emergencies, and explains what a plumber does on the visit.
What you notice
- The toilet runs continuously or turns itself on for a few seconds every so often.
- A weak or incomplete flush, or the bowl fills high before it drains slowly.
- The bowl overflows or threatens to when flushed.
- Water on the floor around the base, or a soft, discolored floor near the toilet.
- The toilet rocks when you sit on it.
- Hissing, whistling or a thud from the tank after the flush.
Likely causes
A worn flapper
The rubber flapper at the bottom of the tank seals the water in between flushes. When it warps or scales up, water leaks into the bowl, the level drops, and the fill valve kicks on to top it up. This is the leading cause of a toilet that runs on and off.
A failed or misadjusted fill valve
The fill valve refills the tank and shuts off at a set level. If it is set too high or has worn, water runs over the overflow tube and the toilet never stops. A hissing tank is usually a fill valve.
A clog in the trap or the drain line
Too much paper, wipes or an object dropped in the bowl lodges in the toilet’s built-in trap. A clog further down the line shows up as several fixtures draining slowly or the toilet backing up when a tub drains.
A failed wax ring or loose bolts at the base
The wax ring seals the toilet to the drain. If the toilet rocks or the ring has failed, dirty water seeps out at the base with every flush and soaks the subfloor.
Mineral buildup in the rim jets
Hard water scale narrows the small holes under the rim so less water enters the bowl and the flush weakens over time. Common in older toilets.
A cracked tank or bowl
Hairline cracks in the porcelain weep slowly and are easy to miss. A crack in the tank can fail suddenly and flood a bathroom.
Safe things to check before anyone comes out
- Listen to the toilet a few minutes after a flush. Periodic refilling with no one using it points to a leaking flapper.
- Look at the water level in the bowl. Lower than usual suggests a flapper leak or a crack; higher than usual suggests a partial clog.
- Look around the base after a flush for water or a dark ring on the flooring, and press gently on the toilet with your hand to see if it rocks.
- Run water in the nearby sink or tub. If the toilet bubbles or the tub drains slowly, the problem is in the shared drain line, not the toilet.
- Note whether the trouble started after something fell in, after a renovation, or gradually over months.
- If the bowl is near overflowing, do not flush again. Stop using the toilet until it is cleared.
When to stop and call
- Water is spreading from the bathroom toward outlets, a heater or other electrical equipment, or you smell gas. Shut the toilet’s supply valve if you can reach it and move away from the area.
- Sewage is coming up through the toilet, tub or a floor drain. Stop using water in the house and call the same day.
- The toilet overflows every time it is flushed and plunging does not help.
- The tank or bowl is cracked and leaking.
- The floor around the toilet is soft or sagging.
What the technician does
- Watches a flush and refill cycle and lifts the tank lid to see the flapper, fill valve and water level.
- Replaces a worn flapper, fill valve or flush valve. These are common parts that are usually on the truck.
- Clears a clog with a closet auger built for toilets, or runs a drain cable from a cleanout if the blockage is further down.
- Pulls the toilet to replace the wax ring and bolts if it is leaking at the base, checks the flange and subfloor, and resets the toilet level and tight.
- Cleans scaled rim jets or recommends replacement when an older toilet cannot flush well anymore.
- Runs several flushes, checks for leaks at the supply, tank and base, and explains what was wrong and whether the toilet has years left in it.
What it usually costs
Replacing a flapper or fill valve, or clearing a simple clog, is usually a short visit in the low hundreds of dollars including the part. Pulling and resetting a toilet with a new wax ring costs more, and a main-line clog or a replacement toilet more still. The estimate should be explained before any work starts, including any diagnostic or trip fee.
What moves the estimate
- Whether the fix is a tank part, a clog in the toilet or a blockage further down the line.
- Whether the toilet has to be removed to reach the problem.
- Condition of the flange and subfloor if the base has been leaking for a while.
- Age and model: parts for very old or unusual toilets can be hard to find.
- Urgency. Same-day and after-hours visits usually carry a higher rate.
Keeping it from coming back
- Flush only toilet paper. Wipes, paper towels and hygiene products cause most toilet and line clogs even when labeled flushable.
- Replace the flapper every few years, or sooner if the toilet starts running. It is an inexpensive part.
- Skip in-tank chemical cleaners. They degrade rubber parts and shorten the life of the flapper and seals.
- Keep small items off the tank lid. Most objects that end up in a toilet fall from there.
- If the toilet ever rocks, have it reset before the wax ring fails and the floor gets wet.
Questions people ask
Why does the toilet keep running?
Almost always a worn flapper or a fill valve set too high or worn out. Both are quick fixes. A running toilet can waste a lot of water, so it is worth addressing even though it is not urgent.
Can I plunge a clogged toilet?
Yes. A flanged plunger with a firm seal clears many clogs. If the water is near the rim, wait for it to go down first. If plunging does not work after a few tries, or the clog keeps coming back, have it looked at.
Should I use a chemical drain cleaner in the toilet?
No. Caustic cleaners rarely clear a toilet clog, can crack porcelain as they heat up, and leave a hazard for whoever works on it next.
When is it time to replace the toilet instead?
When the porcelain is cracked, when an older model flushes poorly even after cleaning, or when repair parts keep adding up. Newer models use far less water per flush, which can offset part of the cost over time.
Sources
- U.S. EPA WaterSense: Residential toilets www.epa.gov
- U.S. EPA WaterSense: Fix a Leak Week (checking toilet flappers) www.epa.gov
- Fluidmaster: How to fix a running toilet fluidmaster.com
- Fluidmaster: Toilet tank won’t fill or fills slowly fluidmaster.com